题意：给定同一个图上的两种路径，求出从某点出发到另一点的路径长度来回长度之比最大的情况，最后还要输出路径。
1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 #include <cstdlib> 5 #include <algorithm> 6 #include <queue> 7 using namespace std; 8 #define inf 9999999 9 #define N 1005 10 #define M 1005 11 struct Edge 12 { 13 int v,w,next; 14 Edge(){} 15 Edge(int V,int W,int NEXT):v(V),w(W),next(NEXT){} 16 }edge1[M],edge2[M]; 17 int path1[N][N],path2[N][N]; 18 // path1存下坡从i到j的最长路的路径,path2存上坡从i到j的最短路的路径 19 int dis1[N][N],dis2[N][N]; 20 // dis1存下坡从i到j的最长路,dis2存上坡从i到j的最短路 21 int head1[N],head2[N]; 22 int n,m,k,size1,size2,vis[N]; 23 24 void Init() // 初始化 25 { 26 size1 = 0; 27 size2 = 0; 28 memset(head1,-1,sizeof(head1)); 29 memset(head2,-1,sizeof(head2)); 30 } 31 void InsertEdge1(int u,int v,int w) //加下坡的边 32 { 33 edge1[size1] = Edge(v,w,head1[u]); 34 head1[u] = size1++; 35 } 36 void InsertEdge2(int u,int v,int w) //加上坡的边 37 { 38 edge2[size2] = Edge(v,w,head2[u]); 39 head2[u] = size2++; 40 } 41 42 void spfa1(int st,int* head,int* path,int* dis,Edge* edge) //求下坡的最长路 43 { 44 for(int i=1; i<=n; i++) 45 { 46 vis[i] = 0; 47 dis[i] = -1; // 48 path[i] = -1; 49 } 50 vis[st] = 1; dis[st] = 0; 51 queue<int> Q; 52 Q.push(st); 53 while(!Q.empty()) 54 { 55 int u = Q.front(); 56 Q.pop(); 57 vis[u] = 0; 58 for(int i=head[u]; i!=-1; i=edge[i].next) 59 { 60 int v = edge[i].v; 61 if(dis[v] < dis[u] + edge[i].w) // 62 { 63 dis[v] = dis[u] + edge[i].w ; 64 path[v] = u; 65 if(!vis[v]) 66 { 67 vis[v] = 1; 68 Q.push(v); 69 } 70 } 71 } 72 } 73 } 74 75 void spfa2(int st,int* head,int* path,int* dis,Edge* edge) //求上坡最短路 76 { 77 for(int i=1; i<=n; i++) 78 { 79 vis[i] = 0; 80 dis[i] = inf; // 81 path[i] = -1; 82 } 83 vis[st] = 1; dis[st] = 0; 84 queue<int> Q; 85 Q.push(st); 86 while(!Q.empty()) 87 { 88 int u = Q.front(); 89 Q.pop(); 90 vis[u] = 0; 91 for(int i=head[u]; i!=-1; i=edge[i].next) 92 { 93 int v = edge[i].v; 94 if(dis[v] > dis[u] + edge[i].w) // 95 { 96 dis[v] = dis[u] + edge[i].w; 97 path[v] = u; 98 if(!vis[v]) 99 { 100 vis[v] = 1; 101 Q.push(v); 102 } 103 } 104 } 105 } 106 } 107 108 int main() 109 { 110 int T; 111 scanf("%d",&T); 112 while(T--) 113 { 114 scanf("%d%d%d",&n,&m,&k); 115 Init(); 116 int u,v,w; 117 for(int i=0; i<m; i++) 118 { 119 scanf("%d%d%d",&u,&v,&w); 120 InsertEdge1(u,v,w); 121 } 122 for(int i=0; i<k; i++) 123 { 124 scanf("%d%d%d",&u,&v,&w); 125 InsertEdge2(u,v,w); 126 } 127 for(int i=1; i<=n; i++) 128 { 129 spfa1(i,head1,path1[i],dis1[i],edge1); // 对每个点求下坡最长路 130 spfa2(i,head2,path2[i],dis2[i],edge2); // 对每个点求上坡最短路 131 } 132 double ans = 0; 133 int st,ed; 134 for(int i=1; i<=n; i++) //枚举 135 for(int j=1; j<=n; j++) 136 { 137 if(i!=j && dis1[i][j]!=-1 && dis2[j][i] != inf) 138 { 139 double Rate = (1.0*dis1[i][j])/(1.0*dis2[j][i]); 140 if(Rate > ans) 141 { 142 st = i; //记录起点 143 ed = j; //记录终点 144 ans = Rate; //最后输出的值 145 } 146 } 147 } 148 int a1[N],a2[N]; 149 int k1 = 0 , k2 = 0; 150 int S=st,E=ed,d; 151 d = S; 152 while(d!=-1) // 上坡的路径 153 { 154 a2[k2++] = d; 155 d = path2[E][d]; 156 } 157 for(int i=k2-1; i>=0; i--) 158 printf("%d ",a2[i]); 159 d = E; 160 while(d!=-1) //下坡的路径 161 { 162 a1[k1++] = d; 163 d = path1[S][d]; 164 } 165 for(int i=k1-2; i>0; i--) 166 printf("%d ",a1[i]); 167 printf("%d ",a1[0]); 168 printf("%.3f ",ans); 169 } 170 return 0; 171 }